Electronic devices, such as smartphones and tablets are often used in combination with wearable electronic devices, such as wireless headsets or watches. For example, a user may have a smartphone and a watch that are communicatively linked or “paired” to each other via Bluetooth or other wireless communication technologies. A wireless communication link between the smartphone and watch allows for exchanging data between them, but also for estimating their proximity. The smartphone (or watch) may be configured to alert the user when the distance to the paired device reaches a predetermined threshold to prevent the user from leaving the paired device behind, prevent moving the device without the user's knowledge (e.g., being stolen), or to lock either device to prevent unauthorized access when out of range.
The smartphone may estimate a distance between itself and the watch based on a signal strength of a wireless signal received from the watch; however, various factors affect the received signal strength independently from the actual distance. Environmental factors, such as moving between rooms in a house or office building, can increase interference and reduce the received signal strength as the wireless signal must travel through walls and other materials. Moving from an indoor location to an outdoor location can also reduce received signal strength due to fewer multipath signal reflections. Variations in received signal strength caused by environmental factors can cause the smartphone to alert the user, based on the received signal strength, when the actual distance between the smartphone and the watch is within an acceptable range.